Automotive traction control systems have been developed as a stability enhancement feature, and operate to reduce wheel torque in response to a detected wheel spin condition. A number of control variables have been utilized to carry out the torque reduction, including engine fuel reduction, engine spark retard, engine throttle control, and brake controls. In general, detection of the wheel spin condition is achieved by precisely monitoring the speeds of the driven wheels and comparing them with the speeds of un-driven wheels or a vehicle reference speed.
The incremental cost of providing a traction control function is minimized in vehicles having an anti-lock brake system since the required wheel speed and reference speed information is available at little or no additional cost. However, the incremental cost of traction control is much higher in vehicles where anti-lock brake system inputs and variables are not available. Accordingly, it is desired to provide a traction control system that does not require high resolution wheel speed sensors, and yet can be made available at a small incremental cost.